1. Field of the Invention
The present invention relates to an antenna device preferably use in a HF band communication system, for example, and to an electronic appliance.
2. Description of the Related Art
A technology of providing a communication terminal device such as a cellular phone terminal with an RFID function is, for example, disclosed in Japanese Unexamined Patent Application Publication No. 2012-029258. In Japanese Unexamined Patent Application Publication No. 2012-029258, an antenna device is disclosed that includes an antenna, which has a coil portion, and a metal member arranged close to the antenna, an opening portion of the coil portion of the antenna being arranged at an end portion of the metal member.
In a system utilizing a HF band as a communication frequency, the range of communication between antenna devices depends on the magnetic flux passing through the coil antennas. That is, in order to secure a certain communication range between antenna devices, it is necessary to make the size of the coil antennas large but making the size of the coil antennas large impedes the size reduction of electronic appliances such as communication terminal devices.
In the antenna device described in Japanese Unexamined Patent Application Publication No. 2012-029258, an antenna is arranged in which a coil opening portion extends across an end portion of a metal member and therefore there is a tendency for the volume of the antenna to be large and for an electronic appliance to be increased in size. On the other hand, if size reduction of the electronic appliance is a priority and the volume of the volume of the antenna is made small, coupling with the antenna on the communication partner side is weakened.